Controllable Growth of Straight Nanorods and Nanowires in the Langmuir Films of a Bolaamphiphilic PAR Derivative

Abstract

A novel bolaamphiphilic compound, 1, 10-bis[3'-hydroxy-4'-(2''-pyridylazo)phenoloxy] decane [(PAR)2C10], was synthesized and its spreading film and in situ coordination with metal ions in the Langmuir monolayer at the air/water interface were investigated. It was found that (PAR)2C10 could be spread on the water surface, and the Langmuir film showed a phase transition from a flat conformation to a U-shaped conformation upon compression. Interfacial coordination between (PAR)2C10 and metal ions could occur in situ in the Langmuir monolayer. Depending on the concentration of the subphase, different coordination modes were observed. A 2:1 (ligand-PAR-to-metal-ion) complex was formed at a lower concentration of the subphase, while a 1:1 complex was obtained on the subphase with a higher concentration of the salt. Interestingly, very straight nanowires, extending to several micrometers, were observed in the AFM images of the films transferred from the subphase containing CuCl2 in higher concentrations. However, tortuous nanowires were observed under the subphase containing Cu(CH3COO)2. The formation of such kind of wire-like structures was only observed for the combination of the bolaamphiphilic PAR derivative with the Cu(II) ions. Other metal ions or the single-chain PAR derivative did not show this behavior. A possible growth mechanism of the nanowires was proposed based on the coordination of the bolaamphiphilic (PAR)2C10 with the Cu(II) ions as well as with the counteranions.

Investigation of Physico-Chemical Properties of Alkali-TreatedProsopis julifloraFibers

“…[21] The existence of wax or wax-like gist is observed in unsymmetrical vibrations at 2355 cm À1 , and 2928 cm À1 is assigned to the less ordered band of the alkyl chain. [22] The bands observed at 1537 to 1375 cm À1 correspond to the aromatic skeletal vibrations, ring breathing with C-O stretching in lignin. A strong peak at 1057 cm À1 is ascribed to the C-O and O-H stretching vibration pertaining to polysaccharide in cellulose.…”

Degumming of ramie bast fibers by Ca2+-activated composite enzyme

“…2918 cm À1 (CH 2 asymmetric) and 2852 cm À1 (symmetric vibrations) were attributed to the alkyl chain (Guo, Liu, Nakahara, & Ushida, 2006;Snyder, 1967), indicating the existence of the wax or wax-like substances. 2900 (CH and CH 2 stretching vibrations) and 1735 cm À1 (C=O stretching) were ascribed to methyl ester and carboxylic acid in pectin or the acetyl group in hemicelluloses.…”

Evidence for a Reverse U-Shaped Conformation of Single-Chain Bolaamphiphiles at the Air−Water Interface

“…The lyotropic properties of these compounds were investigated in great detail to understand the role of bipolar tetraether lipids in membranes of archaebacteria, the formation of lipid nanotubes (LNTs) as novel host structures, or the design of new, effective small molecule hydrogelators . The investigation of the interfacial properties of bolaamphiphiles has attracted considerable interest mainly due to the possibility of providing a fundamental model for the molecular orientation and packing mode of those molecules at the air−water interface and to study interactions with various substrates from the water subphase. − The interfacial aggregation and the surface morphology of the structures of bolaamphiphiles at the air−water interface were elucidated using a variety of surface sensitive methods such as surface pressure−area (π− A ) isotherms, Brewster angle microscopy (BAM), fluorescence microscopy, epi-fluorescence spectroscopy, and X-ray diffraction (XRD) measurements. The investigations show a strong dependence of the observed surface structures on the size and type of the headgroups and the length, chemical structure, and stiffness of the hydrophobic linker. ,− …”